Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C104

Oral Communications

Anatomic distribution of Bradykinin 2 receptors in the upper rat ureteric smooth muscle corresponded to regions of high sensitivity to Bradykinin

A. Alfituri1,2, T. Burdyga1

1. University of liverpool, Liverpool, United Kingdom. 2. University of Benghazi, Benghazi, Libya.

Bradykinin (BK) is present in the urine and induces inflammatory and contractile responses in the ureter of different animals (Catacutan-Labay 1966; Ribero et al., 2016) by stimulating B2 receptors (Eggerickx et al., 1992), however there are no data existed illustrating the anatomical and functional distribution of B2 receptors in the rat ureter. Frozen sections from the upper, middle and lower ureters of male wistar rats (6-8weeks) that were humanely killed using CO2 anaesthesia followed by cervical dislocation in accordance with the UK legislation were immunostained with anti-B2 receptor antibodies and examined under fluorescent microscope and their level of the expression was calculated using confocal microscope.The ureteric segments were also exposed to cumulative doses of BK (0.1, 0.2, 0.5, 1, 2.5, and 5 μM) for 5 minutes and force was measured using a special apparatus designed by Professor Burdyga (university of liverpool). Immunohistochemical studies revealed homogenous distribution of B2 receptors in the urothelium. While, their expression was significantly higher in the smooth muscles (SMs) of the proximal upper (93%±0.6, n=7), lowest in the middle (41%±0.8, n=9), and modest in the lower part, (51%±0.7, n=11) relative to the urothelium. Force measurement revealed that the upper SMs was much more sensitive than other parts. The threshold concentration, which evoked spontaneous activity was 0.5 μM, while in the middle and the lower segments were 2 to 5μM. In the upper ureter, BK at 0.2μM induced small elevation of the baseline force (7.5±0.5%) and at 0.5μM to 16.4±0.3% which was superimposed by spontaneous phasic contractions, with an average frequency of 1.06±0.6 cycles/min (n=9). At 5μM, BK further increased the baseline force to 38.4± 0.6% superimposed by spontaneous contractions, which appeared either as single phasic contractions or long lasting groups of fused phasic contractions. The middle ureter were significantly less sensitive to BK. In 50-60% of the samples, only high concentration (5μM) produced elevation of the base line force to 6.8 ±0.3% (n=7), which was superimposed by the phasic activity, with an average frequency of 0.9 ±0.1 cycles/min, and in the rest of the samples, without phasic activity. Similarly, the SMs of the lower ureter were also significantly less sensitive to BK. at 0.2μM, BK had little or no effect on the baseline force. In the presence of 0.5μM, the base line force was increased to 3.7±0.2%. At 5μM, BK increased both the tonic contraction to 11.9±0.3% and the phasic contractions to 1.6±0.4 cycles/min (n=6). These data demonstrate a higher level of expression of B2 receptors in the proximal ureter corresponded to areas of increased sensitivity of the rat ureteric smooth muscle to BK.

Where applicable, experiments conform with Society ethical requirements